From 3c42b569d89c8c8122cb9613af09fbda6ea03ba6 Mon Sep 17 00:00:00 2001 From: Tonghao Zhang Date: Mon, 21 Nov 2022 18:05:21 +0800 Subject: [PATCH] bpf: avoid hashtab deadlock with try_lock The commit 20b6cc34ea74 ("bpf: Avoid hashtab deadlock with map_locked"), try to fix deadlock, but in some case, the deadlock occurs: * CPUn in task context with K1, and taking lock. * CPUn interrupted by NMI context, with K2. * They are using the same bucket, but different map_locked. | Task | +---v----+ | CPUn | +---^----+ | | NMI Anyway, the lockdep still warn: [ 36.092222] ================================ [ 36.092230] WARNING: inconsistent lock state [ 36.092234] 6.1.0-rc5+ #81 Tainted: G E [ 36.092236] -------------------------------- [ 36.092237] inconsistent {INITIAL USE} -> {IN-NMI} usage. [ 36.092238] perf/1515 [HC1[1]:SC0[0]:HE0:SE1] takes: [ 36.092242] ffff888341acd1a0 (&htab->lockdep_key){....}-{2:2}, at: htab_lock_bucket+0x4d/0x58 [ 36.092253] {INITIAL USE} state was registered at: [ 36.092255] mark_usage+0x1d/0x11d [ 36.092262] __lock_acquire+0x3c9/0x6ed [ 36.092266] lock_acquire+0x23d/0x29a [ 36.092270] _raw_spin_lock_irqsave+0x43/0x7f [ 36.092274] htab_lock_bucket+0x4d/0x58 [ 36.092276] htab_map_delete_elem+0x82/0xfb [ 36.092278] map_delete_elem+0x156/0x1ac [ 36.092282] __sys_bpf+0x138/0xb71 [ 36.092285] __do_sys_bpf+0xd/0x15 [ 36.092288] do_syscall_64+0x6d/0x84 [ 36.092291] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 36.092295] irq event stamp: 120346 [ 36.092296] hardirqs last enabled at (120345): [] _raw_spin_unlock_irq+0x24/0x39 [ 36.092299] hardirqs last disabled at (120346): [] generic_exec_single+0x40/0xb9 [ 36.092303] softirqs last enabled at (120268): [] __do_softirq+0x347/0x387 [ 36.092307] softirqs last disabled at (120133): [] __irq_exit_rcu+0x67/0xc6 [ 36.092311] [ 36.092311] other info that might help us debug this: [ 36.092312] Possible unsafe locking scenario: [ 36.092312] [ 36.092313] CPU0 [ 36.092313] ---- [ 36.092314] lock(&htab->lockdep_key); [ 36.092315] [ 36.092316] lock(&htab->lockdep_key); [ 36.092318] [ 36.092318] *** DEADLOCK *** [ 36.092318] [ 36.092318] 3 locks held by perf/1515: [ 36.092320] #0: ffff8881b9805cc0 (&cpuctx_mutex){+.+.}-{4:4}, at: perf_event_ctx_lock_nested+0x8e/0xba [ 36.092327] #1: ffff8881075ecc20 (&event->child_mutex){+.+.}-{4:4}, at: perf_event_for_each_child+0x35/0x76 [ 36.092332] #2: ffff8881b9805c20 (&cpuctx_lock){-.-.}-{2:2}, at: perf_ctx_lock+0x12/0x27 [ 36.092339] [ 36.092339] stack backtrace: [ 36.092341] CPU: 0 PID: 1515 Comm: perf Tainted: G E 6.1.0-rc5+ #81 [ 36.092344] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 [ 36.092349] Call Trace: [ 36.092351] [ 36.092354] dump_stack_lvl+0x57/0x81 [ 36.092359] lock_acquire+0x1f4/0x29a [ 36.092363] ? handle_pmi_common+0x13f/0x1f0 [ 36.092366] ? htab_lock_bucket+0x4d/0x58 [ 36.092371] _raw_spin_lock_irqsave+0x43/0x7f [ 36.092374] ? htab_lock_bucket+0x4d/0x58 [ 36.092377] htab_lock_bucket+0x4d/0x58 [ 36.092379] htab_map_update_elem+0x11e/0x220 [ 36.092386] bpf_prog_f3a535ca81a8128a_bpf_prog2+0x3e/0x42 [ 36.092392] trace_call_bpf+0x177/0x215 [ 36.092398] perf_trace_run_bpf_submit+0x52/0xaa [ 36.092403] ? x86_pmu_stop+0x97/0x97 [ 36.092407] perf_trace_nmi_handler+0xb7/0xe0 [ 36.092415] nmi_handle+0x116/0x254 [ 36.092418] ? x86_pmu_stop+0x97/0x97 [ 36.092423] default_do_nmi+0x3d/0xf6 [ 36.092428] exc_nmi+0xa1/0x109 [ 36.092432] end_repeat_nmi+0x16/0x67 [ 36.092436] RIP: 0010:wrmsrl+0xd/0x1b [ 36.092441] Code: 04 01 00 00 c6 84 07 48 01 00 00 01 5b e9 46 15 80 00 5b c3 cc cc cc cc c3 cc cc cc cc 48 89 f2 89 f9 89 f0 48 c1 ea 20 0f 30 <66> 90 c3 cc cc cc cc 31 d2 e9 2f 04 49 00 0f 1f 44 00 00 40 0f6 [ 36.092443] RSP: 0018:ffffc900043dfc48 EFLAGS: 00000002 [ 36.092445] RAX: 000000000000000f RBX: ffff8881b96153e0 RCX: 000000000000038f [ 36.092447] RDX: 0000000000000007 RSI: 000000070000000f RDI: 000000000000038f [ 36.092449] RBP: 000000070000000f R08: ffffffffffffffff R09: ffff8881053bdaa8 [ 36.092451] R10: ffff8881b9805d40 R11: 0000000000000005 R12: ffff8881b9805c00 [ 36.092452] R13: 0000000000000000 R14: 0000000000000000 R15: ffff8881075ec970 [ 36.092460] ? wrmsrl+0xd/0x1b [ 36.092465] ? wrmsrl+0xd/0x1b [ 36.092469] [ 36.092469] [ 36.092470] __intel_pmu_enable_all.constprop.0+0x7c/0xaf [ 36.092475] event_function+0xb6/0xd3 [ 36.092478] ? cpu_to_node+0x1a/0x1a [ 36.092482] ? cpu_to_node+0x1a/0x1a [ 36.092485] remote_function+0x1e/0x4c [ 36.092489] generic_exec_single+0x48/0xb9 [ 36.092492] ? __lock_acquire+0x666/0x6ed [ 36.092497] smp_call_function_single+0xbf/0x106 [ 36.092499] ? cpu_to_node+0x1a/0x1a [ 36.092504] ? kvm_sched_clock_read+0x5/0x11 [ 36.092508] ? __perf_event_task_sched_in+0x13d/0x13d [ 36.092513] cpu_function_call+0x47/0x69 [ 36.092516] ? perf_event_update_time+0x52/0x52 [ 36.092519] event_function_call+0x89/0x117 [ 36.092521] ? __perf_event_task_sched_in+0x13d/0x13d [ 36.092526] ? _perf_event_disable+0x4a/0x4a [ 36.092528] perf_event_for_each_child+0x3d/0x76 [ 36.092532] ? _perf_event_disable+0x4a/0x4a [ 36.092533] _perf_ioctl+0x564/0x590 [ 36.092537] ? __lock_release+0xd5/0x1b0 [ 36.092543] ? perf_event_ctx_lock_nested+0x8e/0xba [ 36.092547] perf_ioctl+0x42/0x5f [ 36.092551] vfs_ioctl+0x1e/0x2f [ 36.092554] __do_sys_ioctl+0x66/0x89 [ 36.092559] do_syscall_64+0x6d/0x84 [ 36.092563] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 36.092566] RIP: 0033:0x7fe7110f362b [ 36.092569] Code: 0f 1e fa 48 8b 05 5d b8 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 2d b8 2c 00 f7 d8 64 89 018 [ 36.092570] RSP: 002b:00007ffebb8e4b08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 36.092573] RAX: ffffffffffffffda RBX: 0000000000002400 RCX: 00007fe7110f362b [ 36.092575] RDX: 0000000000000000 RSI: 0000000000002400 RDI: 0000000000000013 [ 36.092576] RBP: 00007ffebb8e4b40 R08: 0000000000000001 R09: 000055c1db4a5b40 [ 36.092577] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 36.092579] R13: 000055c1db3b2a30 R14: 0000000000000000 R15: 0000000000000000 [ 36.092586] Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: John Fastabend Cc: KP Singh Cc: Stanislav Fomichev Cc: Hao Luo Cc: Jiri Olsa Signed-off-by: Tonghao Zhang --- kernel/bpf/hashtab.c | 96 +++++++++++++++++--------------------------- 1 file changed, 36 insertions(+), 60 deletions(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 5aa2b5525f793..a47406042a228 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -80,9 +80,6 @@ struct bucket { raw_spinlock_t raw_lock; }; -#define HASHTAB_MAP_LOCK_COUNT 8 -#define HASHTAB_MAP_LOCK_MASK (HASHTAB_MAP_LOCK_COUNT - 1) - struct bpf_htab { struct bpf_map map; struct bpf_mem_alloc ma; @@ -104,7 +101,6 @@ struct bpf_htab { u32 elem_size; /* size of each element in bytes */ u32 hashrnd; struct lock_class_key lockdep_key; - int __percpu *map_locked[HASHTAB_MAP_LOCK_COUNT]; }; /* each htab element is struct htab_elem + key + value */ @@ -146,35 +142,26 @@ static void htab_init_buckets(struct bpf_htab *htab) } } -static inline int htab_lock_bucket(const struct bpf_htab *htab, - struct bucket *b, u32 hash, +static inline int htab_lock_bucket(struct bucket *b, unsigned long *pflags) { unsigned long flags; - hash = hash & HASHTAB_MAP_LOCK_MASK; - - preempt_disable(); - if (unlikely(__this_cpu_inc_return(*(htab->map_locked[hash])) != 1)) { - __this_cpu_dec(*(htab->map_locked[hash])); - preempt_enable(); - return -EBUSY; + if (in_nmi()) { + if (!raw_spin_trylock_irqsave(&b->raw_lock, flags)) + return -EBUSY; + } else { + raw_spin_lock_irqsave(&b->raw_lock, flags); } - raw_spin_lock_irqsave(&b->raw_lock, flags); *pflags = flags; - return 0; } -static inline void htab_unlock_bucket(const struct bpf_htab *htab, - struct bucket *b, u32 hash, +static inline void htab_unlock_bucket(struct bucket *b, unsigned long flags) { - hash = hash & HASHTAB_MAP_LOCK_MASK; raw_spin_unlock_irqrestore(&b->raw_lock, flags); - __this_cpu_dec(*(htab->map_locked[hash])); - preempt_enable(); } static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node); @@ -467,7 +454,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU); bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC); struct bpf_htab *htab; - int err, i; + int err; htab = bpf_map_area_alloc(sizeof(*htab), NUMA_NO_NODE); if (!htab) @@ -512,15 +499,6 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) if (!htab->buckets) goto free_htab; - for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++) { - htab->map_locked[i] = bpf_map_alloc_percpu(&htab->map, - sizeof(int), - sizeof(int), - GFP_USER); - if (!htab->map_locked[i]) - goto free_map_locked; - } - if (htab->map.map_flags & BPF_F_ZERO_SEED) htab->hashrnd = 0; else @@ -548,13 +526,13 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) if (htab->use_percpu_counter) { err = percpu_counter_init(&htab->pcount, 0, GFP_KERNEL); if (err) - goto free_map_locked; + goto free_buckets; } if (prealloc) { err = prealloc_init(htab); if (err) - goto free_map_locked; + goto free_buckets; if (!percpu && !lru) { /* lru itself can remove the least used element, so @@ -567,12 +545,12 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) } else { err = bpf_mem_alloc_init(&htab->ma, htab->elem_size, false); if (err) - goto free_map_locked; + goto free_buckets; if (percpu) { err = bpf_mem_alloc_init(&htab->pcpu_ma, round_up(htab->map.value_size, 8), true); if (err) - goto free_map_locked; + goto free_buckets; } } @@ -580,11 +558,10 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) free_prealloc: prealloc_destroy(htab); -free_map_locked: +free_buckets: if (htab->use_percpu_counter) percpu_counter_destroy(&htab->pcount); - for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++) - free_percpu(htab->map_locked[i]); + bpf_map_area_free(htab->buckets); bpf_mem_alloc_destroy(&htab->pcpu_ma); bpf_mem_alloc_destroy(&htab->ma); @@ -781,7 +758,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node) b = __select_bucket(htab, tgt_l->hash); head = &b->head; - ret = htab_lock_bucket(htab, b, tgt_l->hash, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) return false; @@ -792,7 +769,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node) break; } - htab_unlock_bucket(htab, b, tgt_l->hash, flags); + htab_unlock_bucket(b, flags); return l == tgt_l; } @@ -1106,7 +1083,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value, */ } - ret = htab_lock_bucket(htab, b, hash, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) return ret; @@ -1151,7 +1128,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value, } ret = 0; err: - htab_unlock_bucket(htab, b, hash, flags); + htab_unlock_bucket(b, flags); return ret; } @@ -1197,7 +1174,7 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value, copy_map_value(&htab->map, l_new->key + round_up(map->key_size, 8), value); - ret = htab_lock_bucket(htab, b, hash, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) return ret; @@ -1218,7 +1195,7 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value, ret = 0; err: - htab_unlock_bucket(htab, b, hash, flags); + htab_unlock_bucket(b, flags); if (ret) htab_lru_push_free(htab, l_new); @@ -1254,7 +1231,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key, b = __select_bucket(htab, hash); head = &b->head; - ret = htab_lock_bucket(htab, b, hash, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) return ret; @@ -1279,7 +1256,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key, } ret = 0; err: - htab_unlock_bucket(htab, b, hash, flags); + htab_unlock_bucket(b, flags); return ret; } @@ -1320,7 +1297,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key, return -ENOMEM; } - ret = htab_lock_bucket(htab, b, hash, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) return ret; @@ -1344,7 +1321,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key, } ret = 0; err: - htab_unlock_bucket(htab, b, hash, flags); + htab_unlock_bucket(b, flags); if (l_new) bpf_lru_push_free(&htab->lru, &l_new->lru_node); return ret; @@ -1383,7 +1360,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key) b = __select_bucket(htab, hash); head = &b->head; - ret = htab_lock_bucket(htab, b, hash, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) return ret; @@ -1396,7 +1373,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key) ret = -ENOENT; } - htab_unlock_bucket(htab, b, hash, flags); + htab_unlock_bucket(b, flags); return ret; } @@ -1419,7 +1396,7 @@ static int htab_lru_map_delete_elem(struct bpf_map *map, void *key) b = __select_bucket(htab, hash); head = &b->head; - ret = htab_lock_bucket(htab, b, hash, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) return ret; @@ -1430,7 +1407,7 @@ static int htab_lru_map_delete_elem(struct bpf_map *map, void *key) else ret = -ENOENT; - htab_unlock_bucket(htab, b, hash, flags); + htab_unlock_bucket(b, flags); if (l) htab_lru_push_free(htab, l); return ret; @@ -1493,7 +1470,6 @@ static void htab_map_free_timers(struct bpf_map *map) static void htab_map_free(struct bpf_map *map) { struct bpf_htab *htab = container_of(map, struct bpf_htab, map); - int i; /* bpf_free_used_maps() or close(map_fd) will trigger this map_free callback. * bpf_free_used_maps() is called after bpf prog is no longer executing. @@ -1515,10 +1491,10 @@ static void htab_map_free(struct bpf_map *map) bpf_map_area_free(htab->buckets); bpf_mem_alloc_destroy(&htab->pcpu_ma); bpf_mem_alloc_destroy(&htab->ma); + if (htab->use_percpu_counter) percpu_counter_destroy(&htab->pcount); - for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++) - free_percpu(htab->map_locked[i]); + lockdep_unregister_key(&htab->lockdep_key); bpf_map_area_free(htab); } @@ -1562,7 +1538,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key, b = __select_bucket(htab, hash); head = &b->head; - ret = htab_lock_bucket(htab, b, hash, &bflags); + ret = htab_lock_bucket(b, &bflags); if (ret) return ret; @@ -1600,7 +1576,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key, free_htab_elem(htab, l); } - htab_unlock_bucket(htab, b, hash, bflags); + htab_unlock_bucket(b, bflags); if (is_lru_map && l) htab_lru_push_free(htab, l); @@ -1718,7 +1694,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map, head = &b->head; /* do not grab the lock unless need it (bucket_cnt > 0). */ if (locked) { - ret = htab_lock_bucket(htab, b, batch, &flags); + ret = htab_lock_bucket(b, &flags); if (ret) { rcu_read_unlock(); bpf_enable_instrumentation(); @@ -1741,7 +1717,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map, /* Note that since bucket_cnt > 0 here, it is implicit * that the locked was grabbed, so release it. */ - htab_unlock_bucket(htab, b, batch, flags); + htab_unlock_bucket(b, flags); rcu_read_unlock(); bpf_enable_instrumentation(); goto after_loop; @@ -1752,7 +1728,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map, /* Note that since bucket_cnt > 0 here, it is implicit * that the locked was grabbed, so release it. */ - htab_unlock_bucket(htab, b, batch, flags); + htab_unlock_bucket(b, flags); rcu_read_unlock(); bpf_enable_instrumentation(); kvfree(keys); @@ -1813,7 +1789,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map, dst_val += value_size; } - htab_unlock_bucket(htab, b, batch, flags); + htab_unlock_bucket(b, flags); locked = false; while (node_to_free) {